Electrical measuring instrument.



Patente -A r. 29, I902.

(Application filed J m. 2, 1900. Renewed Jan. 6, 1902.)

(No Model.)

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UNITED STATES MATENT OFFICE.

THOMAS DUNCAN, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE SIEMENS & HALSKEELECTRIC COMPANY OF AMERICA, OF CHICAGO, ILLINOIS, A

CORPORATION OF ILLINOIS.

ELECTRICAL MEASURING INSTRUMENT.

SEEGIEIGAEION forming part of Letters Patent No. 698,687, dated April29, 1902.

Application filed January 2, 1900. Renewed January 6, 1902. Serial No.88,493. (No model.)

To aZZ whom, it may concern.-

Be it known thatI, THOMAS DUNCAN, acitizen of the United States,residing at Chicago, in the county of Cook and State of Illinois, haveinvented a certain new and useful Improvement in Electrical MeasuringInstruments, (Case No. 353,) of which the following is a full, clear,concise, and exact description, reference being had to the accompanyingdrawings, forming a part of this specification.

My invention relates to compensating voltmeters, and has for its objectthe provision of improved means for determining the electromotive forceat any predetermined point of a system of distribution, my invent-ionenabling me to accurately secure this result.

l/Vhen the pressure at any point distant from the generating-station isaccurately determined, this pressure may be maintained constant byregulation of the impressed pressure to compensate for load changes andthe O R drop over the distribution-lines due thereto, which variesdirectly as the load.

A method heretofore frequently employed for measuring the pressure atpoints distant from the generating-station in both alternating anddirect current systems of distribution consisted in extending twopressure -wires from the distant point to the generating-station andthere connecting the same with a voltmeter. WVhen the distance to thedistant predetermined point is'great, the expense of these pressurewires is significant when a great number of machines are used. It hasalso been the practicein measuring potential at distant points from agenerating-station in altern ating-current systems of distribution toemploy a voltmeter connected in circuit with the secondary coils oftransformers whose primaries are respectively included in series withthe main transmission-line and between thetransmission-lines.Thislattermethodis, however, objectionable, since a true compensation isnot always effected in the meter for the C R drop, since the effect ofthe series winding would be the same irrespective of the distance of theload from the generator;

In my application Serial No. 93, filed of even date herewith, I havedisclosed a meter provided wlth two windings, one for interpositionbetween the generator-terminals at the generator-station and the otherfor interposition between a point near the generatingstation and adistant point of the line, whereby a pressure-wire leading to thedistant point is dispensed with. By means of the apparatus disclosed inmy said copending application I am enabled accurately to determine thepressure at the predetermined distant point of the transmission-circuit.It is the object of my present invention to secure the results obtainedby my said copending application by the use of a voltmeter, which mayhave a single pressure-winding and which may be so connected in circuitthat the instrument will indicate correctly the pressure at thepredetermined point, so that any ordinary voltmeter may be employed tosecure the desired measurement; and, generally speaking, my inventionresides in means for accomplishing this result.

In practicing the invention I prefer to supply the winding of themeterwith current conveyed from a conductor in a bridge of thetransmission-conductors and also with current conveyed in a conductorbetween apoint of a transmission-conductor near the generator and adistant point of the distributioncircuit.

I will explain my invention more particularly by reference to theaccompanying drawings, illustrating the preferred embodiment thereof, inwhich- Figure lillustrates a system of alternatingcurrent distributionwith a measuring apparatus connected in circuit therewith in accordancewith the invention. Fig. 2 is a detailed View illustrating amodification of the apparatus shown in Fig. 1.

Like parts are indicated by similar characters of reference.

I have shown an alternating-current generator 1 as supplying current totranslating devices 2. The voltmeter 3 may be of any well-knownconstruction. I have indicated the winding 4 thereof in dotted lines anda pointer 5, actuated by the winding,which may be movable. A scale 6 isshownfupon which the pointer may indicate measurements. Transformers 7and 8 are illustrated whose primaries are connected, respectively,between the transmission-conductors of the system at thegenerator-terminals and in a con duct'or 9, connected between a pointnear the generator and a second and distant point 10 of thetransmission-circuit. I preferably include the primary of transformer 8in bridge between the transmission conductors, one

point of connection being with one transmis-fl half the O R dropt'. e.,E where R equals the total resistance of the transmissionconductorsbetween the generating-station and the distant point, E the impressedpres sure, and G the current traversing the transmission-conductors.Forexample,ifthegenerator impressed pressure is one thousand volts andthe total C R drop is ten per cent. for a given load at thepredetermined distant point the primary winding of transformer 8 will besubject to a pressure equaling 100 100O 950 volts. I thereforepreferably so adjust the windings of the transformers that the ratio oftransformation of transformer 8 is one-half that of transformer 7.

The secondaries of the transformers are included, preferably, in serieswith each other and with the winding 4 of the meter. The secondarywindings of the transformers are preferably so connected that theelectromotive forces due thereto oppose each other, whereby the winding4 of the meter will be subject to an electromotive force which is theresultant of electromotive forces in the said secondary coils, thisresultant electromotive force being proportional to the pressure at thepredetermined distant point in the distribution-circuit.

If, for example, the translating devices should be subject to a pressureof one hundred volts in their normal operation, the secondary oftransformer 7 may be wound for one hundred volts pressure and thesecondary of transformer 8 may be Wound for two hundred volts pressure,these coils being opposed. Thus a pressure is generated in the secondaryof transformer 7 equaling one-tenth of the impressed pressure, while a.pressure is generated in the secondary of transformer 8, which is equalto one-fi fth of the impressed pressure minus the total C R drop.

Assuming, again, that the O R drop is ten percent.,although the primaryof transformer 8 is subject to a pressure of nine hundred and fiftyvolts, the pressures which are generated in the secondaries of thetransformers are proportional, respectively, to the impressed pressureand to twice the impressed pressure minus the total C R drop, as theratio vof transformation of transformer 7 is ten to one, while the ratioof transformation of transformer 8 is five to one. The secondary oftransformer? will therefore generate a pres sure of one hundredvolts,while the secondary of transformer 8 will generate a pressure ofone hundred and ninety volts. As these pressures oppose each other, thewinding of the meter is subject to a resultant electromotive force ofninety volts,-which is the pressure at the translating devices at thepoint 10. The needle of the instrument is actuated to indicate thispressure.

Of course the pressures to which the winding of the meter is subjectmayvary in different instruments,'it only being necessary to have thispressureupon the meter-windingproportional to the pressure at thepredetermined distant point. v

In Fig. 2 I have shown a transformer 7, such as is at present employedto reduce the pressure to which the meter-winding is subject and tofurnish current necessary to supply pilot-lamps 11. In practicing myinvention in connection with systems thus equipped I merely add thesmall transformer 8, including the secondary thereof, in series with thesecondary 0f the larger transformer? and the voltmeter-Windingtheelectromotive forces of the secondary windings of the transformers beingopposed.

It is obvious that changesmay readily be made in the apparatus ofmyinvention without departing fromthe spirit thereof, and I do not,therefore, wish to be limited to the precise apparatus herein disclosed;but,

Having thus described my invention, I claim as new and desire to secureby Letters Patent 7 1. In a system of alternating-current distribution,the combination with an alternating-current generator, of twotransformers, one having a primary winding connected in bridge of thedistributing-mains at the generator, and the other havingits primarywinding connected in bridge of the distributingmains, one of theconnections of the latter winding being near the generator and the otherbeing at a point of the transmissioncircuit distant from the generator,and a voltmeter, the secondary coils of the transformers being includedin series with each other and with the voltmeter-Winding, the secondarycoils of the transformers being arranged to have the electromotiveforces generated therein opposed to each other, substantially asdescribed.

2. In a system of alternating-current distribution, the combination withan alternating-current generator, of two transformers, one having itsprimary winding connected in bridge of the distributing-mains at thegenerator, and the other having its primary winding connected in bridgeof the distributingmaius, one of the connections of the latter windingbeing near the generator and the other being at a point of thetransmission-circuit distant from the generator, and a voltmeter, thesecondary coils of the transformers being included in series with eachother and IIO with the voltmeter-winding, substantially as described.

3. In a system of alternating-current dis tribution, the combinationwith an alternating-current generator, of two transformers, one having aprimary winding connected in bridge of the distributing-mains at thegenerator, and the other having its primary winding connected betweendistant points of the transmission system, and a voltmeter, thesecondary coils of the transformers being included in series with eachother and with the voltmeter-windings, substantially as described.

4. In a system of alternating-current dis tribution, the combinationwith an alternating-current generator, of two transformers, one having aprimary winding connected in bridge of the distributing-mains at thegenerator, and the other having its primary winds ing connected betweena point of the transmission-circuit near the generator and a second,distant point of the transmission-circuit, and a voltmeter, thesecondary coils of the transformers being included in series with eachother and with the voltmeter-winding, substantially as described.

5. In a system of alternating-current distribution, the combination withan alternating-current generator, of two transformers, one having itsprimary winding connected in bridge of the distributing-mains at thegenerator, and the other having its primary winding connected in bridgeof the distributingmains, one of the connections of the latter windingbeing near the generator and the other being at a point of thetransmission-circuit distant from the generator, and 21. voltmeter, thesecondary coils of the transformers supplying current to thevoltmeter-winding, the secondary coils of the transformers beingarranged to have the electromotive forces generated therein opposed toeach other, substantially as described.

6. In a system of alternating-current distribution, the combination withan alternating-current generator, of two transformers, one having itsprimary winding connected in bridge of the distributing-mains at thegenerator, and the other having its primary winding connected in bridgeof the distributingmains, one of the connections of the latter windingbeing near thegenerator and the other being at a point of thetransmission-circuit distant from the generator, and a voltmeter, thesecondary coils of the transformers supplying current to thevoltmeter-winding, substantially as described.

7. In a system of alternating-current-distribution, the combination withan alternating-current generator, of two transformers, one having aprimary winding connected in bridge of the distributing-mains at thegenorator, and the other having its primary winding connected betweendistant points of the transmission system, and a voltmeter, the

secondary coils of the transformers supplying current'to thevoltmeter-winding, substantially as described.

8. In a system of alternating-current distribution, the combination withan'alternat ing-current generator, of two transformers, one having aprimary winding connected in bridge of the distributing-mains at the generator, and the other having its primary winding connected between apoint of the transmission-circuit near the generator, andafsecond',distant point of the transmission-circuit, and a voltmeter,the secondary coils of the transformers supplying current to thevoltmeter-winding, substantially as described. 9. In a system ofelectrical distribution, the combination with a generator supplying thetransmission-circuit, of a voltmeterhaving an operating-Winding, andmeans for subjecting the voltmeter-winding to pressure between thegenerator-terminals and pressure between a point of thetransmission-circuit near the generator and a distant point of thetrausmissiomcircuit, substantially as described.

10. In a system of electrical distribution, the combination, with agenerator supplying the transmission-circuit, of a voltmeter havin g anoperating-winding, and means for subjecting the voltmeter-winding topressure between the generator-terminals andpressure between distantpoints of thedistribution-circuit, substantially'as described.

11. In a system of electrical distribution, the combination, with agenerator supplying the transmission-circuit, of a voltmeter having anoperating-winding, means for subjecting the voltmeter-winding topressure between the generator-terminals and pressure between a point ofthe transmission-circuit near the generator and a distant point of thetransmission-circuit, and means where by the said electromotive forcesare opposed to produce a resultant electromotive force proportional tothe pressure at the distant point to which the said meter-Winding issubject, substantially as described.

12. In a system of electrical distribution,- the combination with agenerator supplying the transmission-circuiuof a voltmeter having anoperating-winding, means for sub jecting the voltmeter-winding topressure between the generator-terminals and pressure between distantpoints of the distribution-circuit,and means whereby the saidelectromotive forces are opposed to produce a resultant electromotiveforce proportional to the pressure at the distant point to which thesaidmeter-winding is subject, substantially as described.

In witness whereof I hereunto subscribe my name this 22d day ofDecember, A. 'D. 1899.:

